A drill tool such as, for example, a drill bit is often used during rock drilling, the drill bit being connected to a drilling machine, in general by means of a drill string consisting of one or more drill rod components. The drilling can be accomplished in various ways, e.g. as rotational drilling where the drill tool is pushed towards the rock at high pressure and then crushes the rock.
Another way of performing the drilling is use of percussive drilling machines, where the drill string is provided with a drill steel shank onto which a piston strikes to transfer percussive pulses to the drill tool via the drill string and then further on to the rock. Percussive drilling is often combined with a rotation of the drill string in order to obtain a drilling where the buttons of the drill bit strikes fresh rock at each stroke (the efficiency of the drilling can be increased by avoiding the buttons of the drill bit from striking holes that have been created by previous strokes. At the same time wear of the drill bit buttons is reduced).
The above drilling methods have in common that the drill remnants, the so called drill cuttings, that are formed during the drilling must be evacuated from the hole so that the drill tool the whole time can work against fresh rock and not waste energy on rock that already has been crushed.
For this reason a flushing medium, such as, for example, compressed air is in general used to flush the drill hole from crushed rock.
The compressed air is obtained from a compressor which, similar to other consumers present at a rock drilling apparatus, is driven by a power source, such as, for example, a combustion engine.
In general, various different consumers are driven by one and the same power source at rock drilling apparatuses, which has the result that the power source at all times must be driven at least at a minimum speed, which is dependent on the consumers being connected to the power source. The speed of the power source must be sufficiently high to ensure that the consumer that at the moment has the highest demand will obtain enough power to ensure desired functionality.
The advantage of such solutions is that one and the same power source can be used as power source for all consumers that are present at the drilling rig, such as compressor, hydraulic pumps/motors, percussion mechanism, etc.
This solution, however, has the disadvantage that many times the actual speed of the power source is not optimal to all consumers. For example, the power demand of the compressor (the demand of compressed air by the rock drilling apparatus) can be lower than the power demand of the percussion mechanism (the hydraulic pump powering the percussion mechanism), which has the result that more power than what is necessary is consumed during a drilling process, with extensive fuel consumption and generation of heat and noise as result.
Consequently there exists a need for an improved control of, consumers at a rock drilling process.